Commit 8c9bb956 authored Dec 08, 2022 by Zhao Wenhui Committed by Zheng Zengkai Dec 08, 2022

sched/fair: limit burst to zero when cfs bandwidth is toggled off

hulk inclusion
category: bugfix
bugzilla: 187464, https://gitee.com/openeuler/kernel/issues/I612GU



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sched/fair: limit burst to zero when cfs bandwidth is toggled off

When the quota value in CFS bandwidth is set to -1, that imples the
cfs bandwidth is toggled off. So the burst feature is supposed to
be disable as well.

Currently, when quota is -1, burst will not be check, so that it can be
set to almost arbitery value. Examples:
        mkdir /sys/fs/cgroup/cpu/test
        echo -1 > /sys/fs/cgroup/cpu/test/cpu.cfs_quota_us
        echo 10000000000000000 > /sys/fs/cgroup/cpu/test/cpu.cfs_burst_us

Moreover, after the burst modified by this way, quota can't be set
to any value:
        echo 100000 > cpu.cfs_quota_us
        -bash: echo: write error: Invalid argument

This patch can ensure the burst value being zero and unalterable,
when quota is set to -1.

Fixes: f4183717 ("sched/fair: Introduce the burstable CFS controller")
Signed-off-by: Zhao Wenhui <zhaowenhui8@huawei.com>
Signed-off-by: Zheng Zucheng <zhengzucheng@huawei.com>
Reviewed-by: Zhang Qiao <zhangqiao22@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>

parent 0d813f1e

kernel/sched/core.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -9120,6 +9120,12 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
		burst + quota > max_cfs_runtime))
		return -EINVAL;

		/*
		* Ensure burst equals to zero when quota is -1.
		*/
		if (quota == RUNTIME_INF && burst)
		return -EINVAL;

		/*
		* Prevent race between setting of cfs_rq->runtime_enabled and
		* unthrottle_offline_cfs_rqs().
		@@ -9179,8 +9185,10 @@ static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)

		period = ktime_to_ns(tg->cfs_bandwidth.period);
		burst = tg->cfs_bandwidth.burst;
		if (cfs_quota_us < 0)
		if (cfs_quota_us < 0) {
		quota = RUNTIME_INF;
		burst = 0;
		}
		else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC)
		quota = (u64)cfs_quota_us * NSEC_PER_USEC;
		else